LOCATION SETILL WAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, isotic, mesic Vitrandic Argixerolls
TYPICAL PEDON: Setill ashy loam, on a south facing 36 percent slope at an elevation of 3,800 feet in a ponderosa pine and Douglas-fir forest. (Colors are for dry soil unless otherwise stated. All textures are apparent field textures.)
Oe--0 to 1 inch; moderately decomposed needles and twigs; abrupt smooth boundary.
A1--1 to 7 inches; dark grayish brown (10YR 4/2) ashy loam, very dark grayish brown (10YR 3/2) moist; moderate fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine and few medium and coarse roots; common fine tubular pores; 5 percent gravel; neutral (pH 7.0); clear smooth boundary. (4 to 7 inches thick)
A2--7 to 11 inches; dark grayish brown (10YR 4/2) ashy loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine and fine and few medium and coarse roots; common fine and very fine tubular pores; 10 percent gravel; neutral (pH 7.0); clear smooth boundary. (1 to 5 inches thick)
BA--11 to 20 inches; brown (10YR 5/3) gravelly ashy loam, dark brown (10YR 3/3) moist; moderate fine and medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine and fine and few medium roots; common very fine and fine pores; 20 percent gravel and 3 percent cobbles; neutral (pH 7.2); clear wavy boundary. (5 to 10 inches thick)
2Bt--20 to 27 inches; brown (10YR 5/3) very gravelly loam; brown (10YR 4/3) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; few very fine irregular pores; few discontinuous faint clay films on faces of peds; 35 percent gravel and 3 percent cobbles; neutral (pH 7.2); clear smooth boundary. (6 to 20 inches thick)
3Btd1--27 to 39 inches; pale brown (10YR 6/3) very gravelly clay loam, brown (10YR 5/3) moist; massive; very hard, firm, moderately sticky and slightly plastic; few very fine roots; few fine irregular pores; few fine and medium irregular shaped yellowish brown (10YR 5/6) stains; few discontinuous faint clay films on faces of peds; 40 percent gravel and 5 percent cobbles; neutral (pH 7.0); gradual wavy boundary.
3Btd2--39 to 61 inches; pale brown (10YR 6/3) very gravelly clay loam, brown (10YR 5/3) moist; massive; very hard, firm, moderately sticky and moderately plastic; few very fine roots; few fine irregular pores; few fine irregular shaped yellowish brown (10YR 5/6) stains; few discontinuous faint clay films on faces of peds; 35 percent gravel and 3 percent cobbles; neutral (pH 7.0).
TYPE LOCATION: Okanogan County, Washington; about 8 miles north of Winthrop, Washington; 2,600 feet east and 2,600 feet north of the southwest corner of section 19, T. 36 N., R. 21 E. (Latitude 48 degrees, 36 minutes, 22 seconds N., Longitude 120 degrees, 15 minutes, 42 seconds W.)
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 47 to 51 degrees F. The soils are usually moist but are dry in all parts between depths at 8 to 24 inches for 75 to 90 consecutive days following the summer solstice. The mollic epipedon is 10 to 20 inches thick and has an estimated moist bulk density of 1.00 to 1.30 g/cc, volcanic glass content of 5 to 20 percent, acid-oxalate extractable aluminum plus one-half of the acid-oxalate extractable iron of 0.4 to 1.0 percent, and 15-bar water retention of 5 to 12 percent for air dried samples. The particle-size control section averages 35 to 50 percent rock fragments and 20 to 35 percent clay. Depth to densic material is 25 to 35 inches.
The A horizon has values of 4 or 5 dry and chroma of 2 or 3 dry. It has 5 to 15 percent gravel.
The BA horizon has values of 4 to 6 dry, 3 to 5 moist, and chroma of 2 to 3 dry or moist. It is gravelly ashy loam or very gravelly ashy loam. It has 15 to 35 percent gravel and 0 to 5 percent cobbles. Reaction ranges from slightly acid to neutral.
The 2Bt horizon has values of 5 or 6 dry, 4 or 5 moist, and chroma of 3 dry and 3 or 4 moist. It is very gravelly loam or very gravelly clay loam. It has 30 to 40 percent gravel and 0 to 10 percent cobbles. Reaction ranges from slightly acid to neutral.
The 3Btd horizon has values of 5 or 6 dry, 4 or 5 moist, and chroma of 3 dry and 3 or 4 moist. It is very gravelly clay loam or very gravelly sandy clay loam. It has 30 to 40 percent gravel and 0 to 10 percent cobbles. Reaction ranges from slightly acid to neutral.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Setill soils are on back slopes and footslopes of mountains and foothills. Elevation ranges from 3,000 to 4,400 feet. These soils formed in glacial till from sedimentary and volcanic rock with a component of volcanic ash in the upper part. Slopes range from 15 to 65 percent. Climate is characterized by hot, dry summers and mild, moist winters. The average annual precipitation is 15 to 18 inches. The average January temperature ranges from 23 to 28 degrees F.; The average July temperature ranges from 63 to 68 degrees F.; and the average annual temperature is 45 to 50 degrees F.; and the frost free season ranges from 100 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Buckrock, Cubhill, Santop, and Nicmar soils. The Buckrock soils are on shoulders and ridges and have bedrock at a depth of 10 to 20 inches. Cubhill soils are on the nonforested backslopes and footslopes. Santop soils are on shoulders and upper backslopes, have a frigid temperature regime and are 20 to 40 inches to bedrock. Nicmar soils are on backslopes and footslopes, have a frigid temperature regime and lack a mollic epipedon.
DRAINAGE AND PERMEABILITY: Well drained, medium to very rapid runoff; moderate over slow permeability.
USE AND VEGETATION: Used for timber production, wildlife habitat, recreation, watershed and livestock grazing. Native vegetation is ponderosa pine and Douglas-fir with an understory of arrowleaf balsamroot, antelope bitterbrush, Idaho fescue, beardless wheatgrass, Saskatoon serviceberry and pinegrass.
DISTRIBUTION AND EXTENT: Northcentral Washington. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Okanogan National Forest, Okanogan County, Washington; 2005.
REMARKS: Diagnostic horizon and features in this pedon are:
Mollic epipedon - 1 to 20 inches (A1, A2 and BA horizon)
Argillic horizon - 20 to 27 inches (2Bt)
Dense till at 27 to 61 inches - (3Btd1 and 3Btd2)
PSCS - zone from 20 to 27 inches - (2Bt)